Our interests in this project involve the effects of mutation on development. We have used the mouse skeleton as a model system. Unusual animals are identified by making a number of measurements on a variety of bones. More severe effects are indicated by greater numbers of animals with more extreme measurements. Collectively, measurements define size and shape. At the level of DNA and chromosome structure, the physical nature of induced mutations varies considerably depending on the dose, the reactive properties of the chemical and other factors. Our approach endeavors to provide a quantitative measure of biological damage which can used to evaluate the genetic impact of germinal mutations induced by different environmental agents.